Scalenus medius
origin: posterior tubercles of the transverse process of 2nd to 7th cervical vertebrae; insertion: superior surface of the 1st rib behind subclavian groove; action: acting unilaterally, flexes and rotates cervical vertebrae; raises first rib; when acting bilaterally, flexes the neck; nerve supply: posterior branches of anterior primary rami of C3, C4; lateral muscular … Read more